/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
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 *
 *
 *
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 *
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 *
 *
 *
 */

package java.util;

import java.util.concurrent.atomic.AtomicLong;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.function.DoubleConsumer;
import java.util.stream.StreamSupport;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.DoubleStream;

/**
 * A generator of uniform pseudorandom values applicable for use in
 * (among other contexts) isolated parallel computations that may
 * generate subtasks. Class {@code SplittableRandom} supports methods for
 * producing pseudorandom numbers of type {@code int}, {@code long},
 * and {@code double} with similar usages as for class
 * {@link java.util.Random} but differs in the following ways:
 *
 * <ul>
 *
 * <li>Series of generated values pass the DieHarder suite testing
 * independence and uniformity properties of random number generators.
 * (Most recently validated with <a
 * href="http://www.phy.duke.edu/~rgb/General/dieharder.php"> version
 * 3.31.1</a>.) These tests validate only the methods for certain
 * types and ranges, but similar properties are expected to hold, at
 * least approximately, for others as well. The <em>period</em>
 * (length of any series of generated values before it repeats) is at
 * least 2<sup>64</sup>. </li>
 *
 * <li> Method {@link #split} constructs and returns a new
 * SplittableRandom instance that shares no mutable state with the
 * current instance. However, with very high probability, the
 * values collectively generated by the two objects have the same
 * statistical properties as if the same quantity of values were
 * generated by a single thread using a single {@code
 * SplittableRandom} object.  </li>
 *
 * <li>Instances of SplittableRandom are <em>not</em> thread-safe.
 * They are designed to be split, not shared, across threads. For
 * example, a {@link java.util.concurrent.ForkJoinTask
 * fork/join-style} computation using random numbers might include a
 * construction of the form {@code new
 * Subtask(aSplittableRandom.split()).fork()}.
 *
 * <li>This class provides additional methods for generating random
 * streams, that employ the above techniques when used in {@code
 * stream.parallel()} mode.</li>
 *
 * </ul>
 *
 * <p>Instances of {@code SplittableRandom} are not cryptographically
 * secure.  Consider instead using {@link java.security.SecureRandom}
 * in security-sensitive applications. Additionally,
 * default-constructed instances do not use a cryptographically random
 * seed unless the {@linkplain System#getProperty system property}
 * {@code java.util.secureRandomSeed} is set to {@code true}.
 *
 * @author Guy Steele
 * @author Doug Lea
 * @since 1.8
 */
public final class SplittableRandom {

    /*
     * Implementation Overview.
     *
     * This algorithm was inspired by the "DotMix" algorithm by
     * Leiserson, Schardl, and Sukha "Deterministic Parallel
     * Random-Number Generation for Dynamic-Multithreading Platforms",
     * PPoPP 2012, as well as those in "Parallel random numbers: as
     * easy as 1, 2, 3" by Salmon, Morae, Dror, and Shaw, SC 2011.  It
     * differs mainly in simplifying and cheapening operations.
     *
     * The primary update step (method nextSeed()) is to add a
     * constant ("gamma") to the current (64 bit) seed, forming a
     * simple sequence.  The seed and the gamma values for any two
     * SplittableRandom instances are highly likely to be different.
     *
     * Methods nextLong, nextInt, and derivatives do not return the
     * sequence (seed) values, but instead a hash-like bit-mix of
     * their bits, producing more independently distributed sequences.
     * For nextLong, the mix64 function is based on David Stafford's
     * (http://zimbry.blogspot.com/2011/09/better-bit-mixing-improving-on.html)
     * "Mix13" variant of the "64-bit finalizer" function in Austin
     * Appleby's MurmurHash3 algorithm (see
     * http://code.google.com/p/smhasher/wiki/MurmurHash3). The mix32
     * function is based on Stafford's Mix04 mix function, but returns
     * the upper 32 bits cast as int.
     *
     * The split operation uses the current generator to form the seed
     * and gamma for another SplittableRandom.  To conservatively
     * avoid potential correlations between seed and value generation,
     * gamma selection (method mixGamma) uses different
     * (Murmurhash3's) mix constants.  To avoid potential weaknesses
     * in bit-mixing transformations, we restrict gammas to odd values
     * with at least 24 0-1 or 1-0 bit transitions.  Rather than
     * rejecting candidates with too few or too many bits set, method
     * mixGamma flips some bits (which has the effect of mapping at
     * most 4 to any given gamma value).  This reduces the effective
     * set of 64bit odd gamma values by about 2%, and serves as an
     * automated screening for sequence constant selection that is
     * left as an empirical decision in some other hashing and crypto
     * algorithms.
     *
     * The resulting generator thus transforms a sequence in which
     * (typically) many bits change on each step, with an inexpensive
     * mixer with good (but less than cryptographically secure)
     * avalanching.
     *
     * The default (no-argument) constructor, in essence, invokes
     * split() for a common "defaultGen" SplittableRandom.  Unlike
     * other cases, this split must be performed in a thread-safe
     * manner, so we use an AtomicLong to represent the seed rather
     * than use an explicit SplittableRandom. To bootstrap the
     * defaultGen, we start off using a seed based on current time
     * unless the java.util.secureRandomSeed property is set. This
     * serves as a slimmed-down (and insecure) variant of SecureRandom
     * that also avoids stalls that may occur when using /dev/random.
     *
     * It is a relatively simple matter to apply the basic design here
     * to use 128 bit seeds. However, emulating 128bit arithmetic and
     * carrying around twice the state add more overhead than appears
     * warranted for current usages.
     *
     * File organization: First the non-public methods that constitute
     * the main algorithm, then the main public methods, followed by
     * some custom spliterator classes needed for stream methods.
     */

  /**
   * The golden ratio scaled to 64bits, used as the initial gamma
   * value for (unsplit) SplittableRandoms.
   */
  private static final long GOLDEN_GAMMA = 0x9e3779b97f4a7c15L;

  /**
   * The least non-zero value returned by nextDouble(). This value
   * is scaled by a random value of 53 bits to produce a result.
   */
  private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53);

  /**
   * The seed. Updated only via method nextSeed.
   */
  private long seed;

  /**
   * The step value.
   */
  private final long gamma;

  /**
   * Internal constructor used by all others except default constructor.
   */
  private SplittableRandom(long seed, long gamma) {
    this.seed = seed;
    this.gamma = gamma;
  }

  /**
   * Computes Stafford variant 13 of 64bit mix function.
   */
  private static long mix64(long z) {
    z = (z ^ (z >>> 30)) * 0xbf58476d1ce4e5b9L;
    z = (z ^ (z >>> 27)) * 0x94d049bb133111ebL;
    return z ^ (z >>> 31);
  }

  /**
   * Returns the 32 high bits of Stafford variant 4 mix64 function as int.
   */
  private static int mix32(long z) {
    z = (z ^ (z >>> 33)) * 0x62a9d9ed799705f5L;
    return (int) (((z ^ (z >>> 28)) * 0xcb24d0a5c88c35b3L) >>> 32);
  }

  /**
   * Returns the gamma value to use for a new split instance.
   */
  private static long mixGamma(long z) {
    z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; // MurmurHash3 mix constants
    z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L;
    z = (z ^ (z >>> 33)) | 1L;                  // force to be odd
    int n = Long.bitCount(z ^ (z >>> 1));       // ensure enough transitions
    return (n < 24) ? z ^ 0xaaaaaaaaaaaaaaaaL : z;
  }

  /**
   * Adds gamma to seed.
   */
  private long nextSeed() {
    return seed += gamma;
  }

  /**
   * The seed generator for default constructors.
   */
  private static final AtomicLong defaultGen = new AtomicLong(initialSeed());

  private static long initialSeed() {
    String pp = java.security.AccessController.doPrivileged(
        new sun.security.action.GetPropertyAction(
            "java.util.secureRandomSeed"));
    if (pp != null && pp.equalsIgnoreCase("true")) {
      byte[] seedBytes = java.security.SecureRandom.getSeed(8);
      long s = (long) (seedBytes[0]) & 0xffL;
      for (int i = 1; i < 8; ++i) {
        s = (s << 8) | ((long) (seedBytes[i]) & 0xffL);
      }
      return s;
    }
    return (mix64(System.currentTimeMillis()) ^
        mix64(System.nanoTime()));
  }

  // IllegalArgumentException messages
  static final String BadBound = "bound must be positive";
  static final String BadRange = "bound must be greater than origin";
  static final String BadSize = "size must be non-negative";

    /*
     * Internal versions of nextX methods used by streams, as well as
     * the public nextX(origin, bound) methods.  These exist mainly to
     * avoid the need for multiple versions of stream spliterators
     * across the different exported forms of streams.
     */

  /**
   * The form of nextLong used by LongStream Spliterators.  If
   * origin is greater than bound, acts as unbounded form of
   * nextLong, else as bounded form.
   *
   * @param origin the least value, unless greater than bound
   * @param bound the upper bound (exclusive), must not equal origin
   * @return a pseudorandom value
   */
  final long internalNextLong(long origin, long bound) {
        /*
         * Four Cases:
         *
         * 1. If the arguments indicate unbounded form, act as
         * nextLong().
         *
         * 2. If the range is an exact power of two, apply the
         * associated bit mask.
         *
         * 3. If the range is positive, loop to avoid potential bias
         * when the implicit nextLong() bound (2<sup>64</sup>) is not
         * evenly divisible by the range. The loop rejects candidates
         * computed from otherwise over-represented values.  The
         * expected number of iterations under an ideal generator
         * varies from 1 to 2, depending on the bound. The loop itself
         * takes an unlovable form. Because the first candidate is
         * already available, we need a break-in-the-middle
         * construction, which is concisely but cryptically performed
         * within the while-condition of a body-less for loop.
         *
         * 4. Otherwise, the range cannot be represented as a positive
         * long.  The loop repeatedly generates unbounded longs until
         * obtaining a candidate meeting constraints (with an expected
         * number of iterations of less than two).
         */

    long r = mix64(nextSeed());
    if (origin < bound) {
      long n = bound - origin, m = n - 1;
      if ((n & m) == 0L)  // power of two
      {
        r = (r & m) + origin;
      } else if (n > 0L) {  // reject over-represented candidates
        for (long u = r >>> 1;            // ensure nonnegative
            u + m - (r = u % n) < 0L;    // rejection check
            u = mix64(nextSeed()) >>> 1) // retry
        {
          ;
        }
        r += origin;
      } else {              // range not representable as long
        while (r < origin || r >= bound) {
          r = mix64(nextSeed());
        }
      }
    }
    return r;
  }

  /**
   * The form of nextInt used by IntStream Spliterators.
   * Exactly the same as long version, except for types.
   *
   * @param origin the least value, unless greater than bound
   * @param bound the upper bound (exclusive), must not equal origin
   * @return a pseudorandom value
   */
  final int internalNextInt(int origin, int bound) {
    int r = mix32(nextSeed());
    if (origin < bound) {
      int n = bound - origin, m = n - 1;
      if ((n & m) == 0) {
        r = (r & m) + origin;
      } else if (n > 0) {
        for (int u = r >>> 1;
            u + m - (r = u % n) < 0;
            u = mix32(nextSeed()) >>> 1) {
          ;
        }
        r += origin;
      } else {
        while (r < origin || r >= bound) {
          r = mix32(nextSeed());
        }
      }
    }
    return r;
  }

  /**
   * The form of nextDouble used by DoubleStream Spliterators.
   *
   * @param origin the least value, unless greater than bound
   * @param bound the upper bound (exclusive), must not equal origin
   * @return a pseudorandom value
   */
  final double internalNextDouble(double origin, double bound) {
    double r = (nextLong() >>> 11) * DOUBLE_UNIT;
    if (origin < bound) {
      r = r * (bound - origin) + origin;
      if (r >= bound) // correct for rounding
      {
        r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
      }
    }
    return r;
  }

    /* ---------------- public methods ---------------- */

  /**
   * Creates a new SplittableRandom instance using the specified
   * initial seed. SplittableRandom instances created with the same
   * seed in the same program generate identical sequences of values.
   *
   * @param seed the initial seed
   */
  public SplittableRandom(long seed) {
    this(seed, GOLDEN_GAMMA);
  }

  /**
   * Creates a new SplittableRandom instance that is likely to
   * generate sequences of values that are statistically independent
   * of those of any other instances in the current program; and
   * may, and typically does, vary across program invocations.
   */
  public SplittableRandom() { // emulate defaultGen.split()
    long s = defaultGen.getAndAdd(2 * GOLDEN_GAMMA);
    this.seed = mix64(s);
    this.gamma = mixGamma(s + GOLDEN_GAMMA);
  }

  /**
   * Constructs and returns a new SplittableRandom instance that
   * shares no mutable state with this instance. However, with very
   * high probability, the set of values collectively generated by
   * the two objects has the same statistical properties as if the
   * same quantity of values were generated by a single thread using
   * a single SplittableRandom object.  Either or both of the two
   * objects may be further split using the {@code split()} method,
   * and the same expected statistical properties apply to the
   * entire set of generators constructed by such recursive
   * splitting.
   *
   * @return the new SplittableRandom instance
   */
  public SplittableRandom split() {
    return new SplittableRandom(nextLong(), mixGamma(nextSeed()));
  }

  /**
   * Returns a pseudorandom {@code int} value.
   *
   * @return a pseudorandom {@code int} value
   */
  public int nextInt() {
    return mix32(nextSeed());
  }

  /**
   * Returns a pseudorandom {@code int} value between zero (inclusive)
   * and the specified bound (exclusive).
   *
   * @param bound the upper bound (exclusive).  Must be positive.
   * @return a pseudorandom {@code int} value between zero (inclusive) and the bound (exclusive)
   * @throws IllegalArgumentException if {@code bound} is not positive
   */
  public int nextInt(int bound) {
    if (bound <= 0) {
      throw new IllegalArgumentException(BadBound);
    }
    // Specialize internalNextInt for origin 0
    int r = mix32(nextSeed());
    int m = bound - 1;
    if ((bound & m) == 0) // power of two
    {
      r &= m;
    } else { // reject over-represented candidates
      for (int u = r >>> 1;
          u + m - (r = u % bound) < 0;
          u = mix32(nextSeed()) >>> 1) {
        ;
      }
    }
    return r;
  }

  /**
   * Returns a pseudorandom {@code int} value between the specified
   * origin (inclusive) and the specified bound (exclusive).
   *
   * @param origin the least value returned
   * @param bound the upper bound (exclusive)
   * @return a pseudorandom {@code int} value between the origin (inclusive) and the bound
   * (exclusive)
   * @throws IllegalArgumentException if {@code origin} is greater than or equal to {@code bound}
   */
  public int nextInt(int origin, int bound) {
    if (origin >= bound) {
      throw new IllegalArgumentException(BadRange);
    }
    return internalNextInt(origin, bound);
  }

  /**
   * Returns a pseudorandom {@code long} value.
   *
   * @return a pseudorandom {@code long} value
   */
  public long nextLong() {
    return mix64(nextSeed());
  }

  /**
   * Returns a pseudorandom {@code long} value between zero (inclusive)
   * and the specified bound (exclusive).
   *
   * @param bound the upper bound (exclusive).  Must be positive.
   * @return a pseudorandom {@code long} value between zero (inclusive) and the bound (exclusive)
   * @throws IllegalArgumentException if {@code bound} is not positive
   */
  public long nextLong(long bound) {
    if (bound <= 0) {
      throw new IllegalArgumentException(BadBound);
    }
    // Specialize internalNextLong for origin 0
    long r = mix64(nextSeed());
    long m = bound - 1;
    if ((bound & m) == 0L) // power of two
    {
      r &= m;
    } else { // reject over-represented candidates
      for (long u = r >>> 1;
          u + m - (r = u % bound) < 0L;
          u = mix64(nextSeed()) >>> 1) {
        ;
      }
    }
    return r;
  }

  /**
   * Returns a pseudorandom {@code long} value between the specified
   * origin (inclusive) and the specified bound (exclusive).
   *
   * @param origin the least value returned
   * @param bound the upper bound (exclusive)
   * @return a pseudorandom {@code long} value between the origin (inclusive) and the bound
   * (exclusive)
   * @throws IllegalArgumentException if {@code origin} is greater than or equal to {@code bound}
   */
  public long nextLong(long origin, long bound) {
    if (origin >= bound) {
      throw new IllegalArgumentException(BadRange);
    }
    return internalNextLong(origin, bound);
  }

  /**
   * Returns a pseudorandom {@code double} value between zero
   * (inclusive) and one (exclusive).
   *
   * @return a pseudorandom {@code double} value between zero (inclusive) and one (exclusive)
   */
  public double nextDouble() {
    return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT;
  }

  /**
   * Returns a pseudorandom {@code double} value between 0.0
   * (inclusive) and the specified bound (exclusive).
   *
   * @param bound the upper bound (exclusive).  Must be positive.
   * @return a pseudorandom {@code double} value between zero (inclusive) and the bound (exclusive)
   * @throws IllegalArgumentException if {@code bound} is not positive
   */
  public double nextDouble(double bound) {
    if (!(bound > 0.0)) {
      throw new IllegalArgumentException(BadBound);
    }
    double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound;
    return (result < bound) ? result : // correct for rounding
        Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1);
  }

  /**
   * Returns a pseudorandom {@code double} value between the specified
   * origin (inclusive) and bound (exclusive).
   *
   * @param origin the least value returned
   * @param bound the upper bound (exclusive)
   * @return a pseudorandom {@code double} value between the origin (inclusive) and the bound
   * (exclusive)
   * @throws IllegalArgumentException if {@code origin} is greater than or equal to {@code bound}
   */
  public double nextDouble(double origin, double bound) {
    if (!(origin < bound)) {
      throw new IllegalArgumentException(BadRange);
    }
    return internalNextDouble(origin, bound);
  }

  /**
   * Returns a pseudorandom {@code boolean} value.
   *
   * @return a pseudorandom {@code boolean} value
   */
  public boolean nextBoolean() {
    return mix32(nextSeed()) < 0;
  }

  // stream methods, coded in a way intended to better isolate for
  // maintenance purposes the small differences across forms.

  /**
   * Returns a stream producing the given {@code streamSize} number
   * of pseudorandom {@code int} values from this generator and/or
   * one split from it.
   *
   * @param streamSize the number of values to generate
   * @return a stream of pseudorandom {@code int} values
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   */
  public IntStream ints(long streamSize) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, streamSize, Integer.MAX_VALUE, 0),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code int}
   * values from this generator and/or one split from it.
   *
   * @return a stream of pseudorandom {@code int} values
   * @implNote This method is implemented to be equivalent to {@code ints(Long.MAX_VALUE)}.
   */
  public IntStream ints() {
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number
   * of pseudorandom {@code int} values from this generator and/or one split
   * from it; each value conforms to the given origin (inclusive) and bound
   * (exclusive).
   *
   * @param streamSize the number of values to generate
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code int} values, each with the given origin (inclusive) and
   * bound (exclusive)
   * @throws IllegalArgumentException if {@code streamSize} is less than zero, or {@code
   * randomNumberOrigin} is greater than or equal to {@code randomNumberBound}
   */
  public IntStream ints(long streamSize, int randomNumberOrigin,
      int randomNumberBound) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * int} values from this generator and/or one split from it; each value
   * conforms to the given origin (inclusive) and bound (exclusive).
   *
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code int} values, each with the given origin (inclusive) and
   * bound (exclusive)
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @implNote This method is implemented to be equivalent to {@code ints(Long.MAX_VALUE,
   * randomNumberOrigin, randomNumberBound)}.
   */
  public IntStream ints(int randomNumberOrigin, int randomNumberBound) {
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.intStream
        (new RandomIntsSpliterator
                (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number
   * of pseudorandom {@code long} values from this generator and/or
   * one split from it.
   *
   * @param streamSize the number of values to generate
   * @return a stream of pseudorandom {@code long} values
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   */
  public LongStream longs(long streamSize) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, streamSize, Long.MAX_VALUE, 0L),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * long} values from this generator and/or one split from it.
   *
   * @return a stream of pseudorandom {@code long} values
   * @implNote This method is implemented to be equivalent to {@code longs(Long.MAX_VALUE)}.
   */
  public LongStream longs() {
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code long} values from this generator and/or one split
   * from it; each value conforms to the given origin (inclusive) and bound
   * (exclusive).
   *
   * @param streamSize the number of values to generate
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code long} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code streamSize} is less than zero, or {@code
   * randomNumberOrigin} is greater than or equal to {@code randomNumberBound}
   */
  public LongStream longs(long streamSize, long randomNumberOrigin,
      long randomNumberBound) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * long} values from this generator and/or one split from it; each value
   * conforms to the given origin (inclusive) and bound (exclusive).
   *
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code long} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @implNote This method is implemented to be equivalent to {@code longs(Long.MAX_VALUE,
   * randomNumberOrigin, randomNumberBound)}.
   */
  public LongStream longs(long randomNumberOrigin, long randomNumberBound) {
    if (randomNumberOrigin >= randomNumberBound) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.longStream
        (new RandomLongsSpliterator
                (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code double} values from this generator and/or one split
   * from it; each value is between zero (inclusive) and one (exclusive).
   *
   * @param streamSize the number of values to generate
   * @return a stream of {@code double} values
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   */
  public DoubleStream doubles(long streamSize) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, streamSize, Double.MAX_VALUE, 0.0),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * double} values from this generator and/or one split from it; each value
   * is between zero (inclusive) and one (exclusive).
   *
   * @return a stream of pseudorandom {@code double} values
   * @implNote This method is implemented to be equivalent to {@code doubles(Long.MAX_VALUE)}.
   */
  public DoubleStream doubles() {
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0),
            false);
  }

  /**
   * Returns a stream producing the given {@code streamSize} number of
   * pseudorandom {@code double} values from this generator and/or one split
   * from it; each value conforms to the given origin (inclusive) and bound
   * (exclusive).
   *
   * @param streamSize the number of values to generate
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code double} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code streamSize} is less than zero
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   */
  public DoubleStream doubles(long streamSize, double randomNumberOrigin,
      double randomNumberBound) {
    if (streamSize < 0L) {
      throw new IllegalArgumentException(BadSize);
    }
    if (!(randomNumberOrigin < randomNumberBound)) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, streamSize, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Returns an effectively unlimited stream of pseudorandom {@code
   * double} values from this generator and/or one split from it; each value
   * conforms to the given origin (inclusive) and bound (exclusive).
   *
   * @param randomNumberOrigin the origin (inclusive) of each random value
   * @param randomNumberBound the bound (exclusive) of each random value
   * @return a stream of pseudorandom {@code double} values, each with the given origin (inclusive)
   * and bound (exclusive)
   * @throws IllegalArgumentException if {@code randomNumberOrigin} is greater than or equal to
   * {@code randomNumberBound}
   * @implNote This method is implemented to be equivalent to {@code doubles(Long.MAX_VALUE,
   * randomNumberOrigin, randomNumberBound)}.
   */
  public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) {
    if (!(randomNumberOrigin < randomNumberBound)) {
      throw new IllegalArgumentException(BadRange);
    }
    return StreamSupport.doubleStream
        (new RandomDoublesSpliterator
                (this, 0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound),
            false);
  }

  /**
   * Spliterator for int streams.  We multiplex the four int
   * versions into one class by treating a bound less than origin as
   * unbounded, and also by treating "infinite" as equivalent to
   * Long.MAX_VALUE. For splits, it uses the standard divide-by-two
   * approach. The long and double versions of this class are
   * identical except for types.
   */
  static final class RandomIntsSpliterator implements Spliterator.OfInt {

    final SplittableRandom rng;
    long index;
    final long fence;
    final int origin;
    final int bound;

    RandomIntsSpliterator(SplittableRandom rng, long index, long fence,
        int origin, int bound) {
      this.rng = rng;
      this.index = index;
      this.fence = fence;
      this.origin = origin;
      this.bound = bound;
    }

    public RandomIntsSpliterator trySplit() {
      long i = index, m = (i + fence) >>> 1;
      return (m <= i) ? null :
          new RandomIntsSpliterator(rng.split(), i, index = m, origin, bound);
    }

    public long estimateSize() {
      return fence - index;
    }

    public int characteristics() {
      return (Spliterator.SIZED | Spliterator.SUBSIZED |
          Spliterator.NONNULL | Spliterator.IMMUTABLE);
    }

    public boolean tryAdvance(IntConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        consumer.accept(rng.internalNextInt(origin, bound));
        index = i + 1;
        return true;
      }
      return false;
    }

    public void forEachRemaining(IntConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        index = f;
        SplittableRandom r = rng;
        int o = origin, b = bound;
        do {
          consumer.accept(r.internalNextInt(o, b));
        } while (++i < f);
      }
    }
  }

  /**
   * Spliterator for long streams.
   */
  static final class RandomLongsSpliterator implements Spliterator.OfLong {

    final SplittableRandom rng;
    long index;
    final long fence;
    final long origin;
    final long bound;

    RandomLongsSpliterator(SplittableRandom rng, long index, long fence,
        long origin, long bound) {
      this.rng = rng;
      this.index = index;
      this.fence = fence;
      this.origin = origin;
      this.bound = bound;
    }

    public RandomLongsSpliterator trySplit() {
      long i = index, m = (i + fence) >>> 1;
      return (m <= i) ? null :
          new RandomLongsSpliterator(rng.split(), i, index = m, origin, bound);
    }

    public long estimateSize() {
      return fence - index;
    }

    public int characteristics() {
      return (Spliterator.SIZED | Spliterator.SUBSIZED |
          Spliterator.NONNULL | Spliterator.IMMUTABLE);
    }

    public boolean tryAdvance(LongConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        consumer.accept(rng.internalNextLong(origin, bound));
        index = i + 1;
        return true;
      }
      return false;
    }

    public void forEachRemaining(LongConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        index = f;
        SplittableRandom r = rng;
        long o = origin, b = bound;
        do {
          consumer.accept(r.internalNextLong(o, b));
        } while (++i < f);
      }
    }

  }

  /**
   * Spliterator for double streams.
   */
  static final class RandomDoublesSpliterator implements Spliterator.OfDouble {

    final SplittableRandom rng;
    long index;
    final long fence;
    final double origin;
    final double bound;

    RandomDoublesSpliterator(SplittableRandom rng, long index, long fence,
        double origin, double bound) {
      this.rng = rng;
      this.index = index;
      this.fence = fence;
      this.origin = origin;
      this.bound = bound;
    }

    public RandomDoublesSpliterator trySplit() {
      long i = index, m = (i + fence) >>> 1;
      return (m <= i) ? null :
          new RandomDoublesSpliterator(rng.split(), i, index = m, origin, bound);
    }

    public long estimateSize() {
      return fence - index;
    }

    public int characteristics() {
      return (Spliterator.SIZED | Spliterator.SUBSIZED |
          Spliterator.NONNULL | Spliterator.IMMUTABLE);
    }

    public boolean tryAdvance(DoubleConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        consumer.accept(rng.internalNextDouble(origin, bound));
        index = i + 1;
        return true;
      }
      return false;
    }

    public void forEachRemaining(DoubleConsumer consumer) {
      if (consumer == null) {
        throw new NullPointerException();
      }
      long i = index, f = fence;
      if (i < f) {
        index = f;
        SplittableRandom r = rng;
        double o = origin, b = bound;
        do {
          consumer.accept(r.internalNextDouble(o, b));
        } while (++i < f);
      }
    }
  }

}
